Cal, during the war years most of the Altec 15" baskets and all of the 12" (I think) were stamped steel, as all available aluminum was going into aircraft. Altec purchased these parts from Utah, who also produced drivers from the same parts during that period. Jim Lansing had begun his speaker business in Salt Lake City in the mid 1920s when Utah was still located there, so the business relationship may have been established then.

If anyone wants to learn more about the field coil Altec Lansing 601 and see some pictures, have a look at this thread:

Holy grail driver

BTW, the 601's horn was made much like the tar filled horns of the time only in miniature. Each cell was soldered together from sheet metal, with a beautiful brass throat casting. This horn is dimensionally similar to the 604 and 604B horn which followed soon after.